// add() 的语法arraylist.add(intindex,E element)// set() 的语法arraylist.set(intindex,E element) 这两种方法都将新元素添加到数组中。 但是,它们之间有很大的不同: set() 方法在指定位置对元素进行更新。 add() 方法将元素插入到指定位置的动态数组中。 实例 import
In the above example, we have created an arraylist namedlanguages. Here, we have used theset()method to replace the element at index1(English) withJava. Note: If you are not sure about the index number of an element, you can use theArrayList indexOf()method. ArrayList set() Vs. add(...
// Call set method to replace the element D with a null element at position 3. al.set(3, null); System.out.println(al); } } Output: [A, B, C, D, null, D] [A, B, C, null, D] [A, B, C, D] [A, B, C, null] 在此示例程序中,您将观察到,当从数组中删除或删除元素...
intMap(200);//method 1: Map.Keyset()longendTime=0;StringstuStr="";// key used to be set when listing map.Studentstu=null;// value used to be set when listing map.longstartTime=System.currentTimeMillis();for(String stuKey : stuMap.keySet()) { stuStr = stuKey; stu = stuMap.get...
java集合【8】-- ArrayList接口源码解析 1. ArrayList ArrayList是最最常用的集合类了,真的没有之一。下面的分析是基于1.8.0_261源码进行分析的。 1.1 ArrayList特点介绍 动态数组,使用的时候,只需要操作即可,内部已经实现扩容机制。 线程不安全 有顺序,会按照添加进去的顺序排好...
Method Summary All MethodsInstance MethodsConcrete Methods Modifier and TypeMethodDescription booleanadd(Ee) Appends the specified element to the end of this list. voidadd(int index,Eelement) Inserts the specified element at the specified position in this list. ...
import java.util.ArrayList; public class Main { public static void main(String[] args) { ArrayList<String> cars = new ArrayList<String>(); cars.add("Volvo"); cars.add("BMW"); cars.add("Ford"); cars.add("Mazda"); System.out.println( cars.subList(1, 3) ); } } ...
HashSet是Java中的另一个集合类,它实现了Set接口,用于存储不重复的元素。HashSet使用哈希表来存储元素,不保证元素的顺序。 下面是一个使用HashSet存储学生对象的示例代码: importjava.util.HashSet;publicclassStudent{privateStringname;privateintage;publicStudent(Stringname,intage){this.name=name;this.age=age;}...
In this tutorial you will learn how to convert ArrayList to Array inJava. 在本教程中,您将学习如何在Java中将ArrayList转换为Array。 Mainly there are two ways to convert ArrayList to array. 主要有两种将ArrayList转换为数组的方法。 Using manual way 使用手动方式 Using toArray() method 使用toArray(...
safe variant ofArrayListin which all mutative operations (add, set, and so on) are implemented by making a fresh copy of the underlying array. This class is very useful when we cannot or do not want to synchronize the traversals of the arraylist. It is part of thread-safe Java ...